[Wi-Fi] Quit worker thread of WifiPickerTracker

Should quit worker thread when a fragment is about to
be destroyed.

Bug: 152454787
Test: make RunSettingsRoboTests ROBOTEST_FILTER=AddAppNetworksFragmentTest
Change-Id: I809511b7f7c092cf9787e8f6bb7c7513c27c98c8

src/com/android/settings/wifi/addappnetworks/AddAppNetworksFragment.java

@@ -124,6 +124,9 @@ public class AddAppNetworksFragment extends InstrumentedFragment implements
     List<Integer> mResultCodeArrayList;
     @VisibleForTesting
     WifiPickerTracker mWifiPickerTracker;
+    // Worker thread used for WifiPickerTracker work
+    @VisibleForTesting
+    HandlerThread mWorkerThread;
 
     private boolean mIsSingleNetwork;
     private boolean mAnyNetworkSavedSuccess;
@@ -133,8 +136,6 @@ public class AddAppNetworksFragment extends InstrumentedFragment implements
     private UiConfigurationItemAdapter mUiConfigurationItemAdapter;
     private WifiManager.ActionListener mSaveListener;
     private WifiManager mWifiManager;
-    // Worker thread used for WifiPickerTracker work
-    private HandlerThread mWorkerThread;
 
     private final Handler mHandler = new Handler() {
         @Override
@@ -202,6 +203,13 @@ public class AddAppNetworksFragment extends InstrumentedFragment implements
         return inflater.inflate(R.layout.wifi_add_app_networks, container, false);
     }
 
+    @Override
+    public void onDestroy() {
+        mWorkerThread.quit();
+
+        super.onDestroy();
+    }
+
     @Override
     public void onViewCreated(View view, Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);